1. Field of the Invention
The present invention relates to an electromagnetically actuated optical deflector.
2. Description of the Related Art
Recently, attention has been paid to an optical deflector manufactured by using a micromachining technique based on a semiconductor manufacturing technique.
The specification of U.S. Pat. No. 6,388,789 discloses, as such an optical deflector, an electromagnetically actuated two-dimensional optical deflector. FIG. 13 is a perspective view of the main part of the optical deflector disclosed in U.S. Pat. No. 6,388,789. FIG. 14 is a sectional perspective view of the optical deflector disclosed in U.S. Pat. No. 6,388,789.
As shown in FIG. 13, this two-dimensional optical deflector includes a first rotating portion 1002, which can rock about the first rotation axis with respect to a support 1001, and a second rotating portion 1003, which can rotate rock the second rotation axis with respect to the first rotating portion 1002. The second rotating portion 1003 has a reflecting surface for reflecting light. The support 1001 and first rotating portion 1002 are coupled to each other through a pair of hinges 1004 and 1004B extending along the first rotation axis. The first rotating portion 1002 and second rotating portion 1003 are coupled to each other through a pair of hinges 1005 and 1005B extending along the second rotation axis.
A pair of first coils 1061 and 1062 for enabling rocking about the first rotation axis and a pair of second coils 1071 and 1072 for enabling rocking about the second rotation axis are formed on the second rotating portion 1003. The first coils 1061 and 1062 are connected to each other through a wiring 1006. The second coils 1071 and 1072 are connected to each other through a wiring 1007. Two wirings 1006A for supplying power to the first coils 1061 and 1062 extend on the pair of hinges 1004 and 1004B, respectively, via the first rotating portion 1002. Likewise, two wirings 1007A for supplying power to the second coils 1071 and 1072 extend on the pair of hinges 1004 and 1004B, respectively, via the first rotating portion 1002.
As shown in FIG. 14, a magnet 1100 is placed below the second rotating portion 1003. The magnet 1100 generates a magnetic field 1089 radially spreading from the center of the second rotating portion 1003 to the support 1001. The second rotating portion 1003 is rocked about the first rotation axis by the interaction between the currents flowing in the first coils 1061 and 1062 and the magnetic field 1089, and also about the second rotation axis by the interaction between the currents flowing in the second coils 1071 and 1072 and the magnetic field 1089.
U.S. Pat. No. 6,404,313 discloses another electromagnetically actuated two-dimensional optical deflector. FIG. 15 is an exploded perspective view of the optical deflector disclosed in U.S. Pat. No. 6,404,313.
As shown in FIG. 15, this two-dimensional optical deflector includes an outer movable plate 2002 located inside a support 2001, an inner movable plate 2003 located inside the outer movable plate 2002, a first torsion bar 2004 supporting the support 2001 so as to allow it to rock about the X-axis with respect to the outer movable plate 2002, and a second torsion bar 2005 supporting the inner movable plate 2003 so as to allow it to rock about the Y-axis with respect to the outer movable plate 2002. The inner movable plate 2003 has a reflecting surface 2104 for reflecting light.
A first driving coil 2102 with a single turn extends on the outer movable plate 2002. A second driving coil 2103 with a single turn extends near a peripheral portion on the inner movable plate 2003. The first driving coil 2102 is connected to the second driving coil 2103.
A pair of magnets 2105 and 2106 are arranged along a diagonal line outside this structure. The magnetic field generated by the magnets 2105 and 2106 exists on one of the diagonal lines. The inner movable plate 2003 is rocked about the X-axis by the interaction between the current flowing in the first driving coil 2102 and the magnetic field, and to rock about the Y-axis by the interaction between the current flowing in the second driving coil 2103 and the magnetic field.